Exhaust structure for combustion apparatus

ABSTRACT

An exhaust structure for a combustion apparatus includes a combustion apparatus, an exhaust tube, an exhaust pipe, an exhaust adapter, and a fixing member. The exhaust tube is connected to the combustion apparatus at the one end portion. A part of the exhaust tube on a side of the other end portion is inserted into the exhaust pipe. The exhaust adapter has an annular shape surrounding a through hole, and is attached to an outer circumferential surface of the exhaust tube and to an inner circumferential surface of the exhaust pipe by inserting the exhaust tube into the through hole. The fixing member is formed of an elastic body, attached to the exhaust pipe at a position close to the combustion apparatus relative to the exhaust adapter, and fixes the exhaust tube to the exhaust pipe while being attached to the outer circumferential surface of the exhaust tube.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an exhaust structure for a combustionapparatus.

2. Description of the Background Art

A combustion apparatus, for example, a heating apparatus, has a mainbody that is placed inside of a building such that an exhaust is emittedthrough an exhaust pipe (a B vent) to the outside of the building. Thereare locations where an already-placed exhaust pipe cannot be removed,from a point of view of maintaining appearance of buildings, when thisalready-placed combustion apparatus should be replaced with a newcombustion apparatus.

At such a location, a new exhaust tube (a flexible exhaust tube) isinserted into the already-placed exhaust pipe without removing thisalready-placed exhaust pipe, so that a combustion apparatus can bereplaced. However, if the exhaust tube has a relatively large outerdiameter, this exhaust tube cannot be placed inside the exhaust pipe.Accordingly, an exhaust tube decreased in diameter needs to be used.

Furthermore, an exhaust tube inserted into the already-placed exhaustpipe needs to be fixed. In general, a grommet is used as a component forfixing a tube. For example, a grommet is disclosed in Japanese PatentLaying-Open Nos. 2002-152949 and 10-92243.

In the case where a new exhaust tube is inserted into the already-placedexhaust pipe from the inside of a building, the exhaust tube should befixed while being inserted into the exhaust pipe; otherwise, there maybe a problem that the exhaust tube falls from inside of the exhaust pipeinto inside of the building.

SUMMARY OF THE INVENTION

The present invention has been made in light of the above-describedproblems. An object of the present invention is to provide an exhauststructure for a combustion apparatus, by which falling of an exhausttube inserted into an exhaust pipe can be prevented.

An exhaust structure for combustion apparatus according to the presentinvention includes a combustion apparatus, an exhaust tube, an exhaustpipe, an exhaust adapter, and a fixing member. The exhaust tube has oneend portion and the other end portion, and is connected to thecombustion apparatus at the one end portion. A part of the exhaust tubeon a side of the other end portion is inserted into the exhaust pipe.The exhaust adapter has an annular shape surrounding a through hole, andis attached to an outer circumferential surface of the exhaust tube andto an inner circumferential surface of the exhaust pipe by inserting theexhaust tube into the through hole. The fixing member is formed of anelastic body, is attached to the exhaust pipe at a position close to thecombustion apparatus relative to the exhaust adapter, and fixes theexhaust tube to the exhaust pipe while being attached to the outercircumferential surface of the exhaust tube.

According to the exhaust structure for combustion apparatus of thepresent invention, the fixing member fixes the exhaust tube to theexhaust pipe in the state where the fixing member is attached to theexhaust pipe and also attached to the outer circumferential surface ofthe exhaust tube. Accordingly, the fixing member can prevent falling ofthe exhaust tube inserted into the exhaust pipe.

Furthermore, the fixing member is attached to the exhaust pipe at aposition close to the combustion apparatus relative to the exhaustadapter. Accordingly, even before attaching the exhaust adapter, thefixing member can prevent falling of the exhaust tube inserted into theexhaust pipe.

In the exhaust structure for combustion apparatus described above, thefixing member includes a first fixing portion attached to the exhausttube; a second fixing portion attached to the exhaust pipe; and a mainbody portion connecting the first fixing portion and the second fixingportion. The main body portion has a communication hole that allowscommunication between a first region and a second region separated fromthe first region by the main body portion. The first region is locatedbetween the outer circumferential surface of the exhaust tube and theinner circumferential surface of the exhaust pipe. Accordingly, when anexhaust leaks to the first region due to damage of the exhaust tube orthe like, the exhaust can be emitted from the first region to the secondregion through the communication hole.

In the exhaust structure for combustion apparatus described above, thefirst fixing portion and the second fixing portion each have acylindrical shape and are concentrically arranged. Accordingly, when theexhaust tube is inserted into the exhaust pipe, the outercircumferential surface of the exhaust tube is less likely to come intocontact with the inner circumferential surface of the exhaust pipe.Consequently, the exhaust tube can be readily inserted into the exhaustpipe.

The exhaust structure for combustion apparatus described above furtherincludes a connection pipe connected to the fixing member and thecombustion apparatus, and into which a part of the exhaust tube on aside of the one end portion is inserted. The second region is providedbetween the outer circumferential surface of the exhaust tube and aninner circumferential surface of the connection pipe. The combustionapparatus includes a housing having an internal space. The housing has aconnection hole that allows communication between the internal space andthe second region. Accordingly, the exhaust tube can be protected by theconnection pipe. Furthermore, when an exhaust leaks to the first regiondue to damage of the exhaust tube and the like, the exhaust can beemitted from the first region through the communication hole to thesecond region provided between the outer circumferential surface of theexhaust tube and the inner circumferential surface of the connectionpipe. Furthermore, the exhaust can be emitted from the second region tothe internal space through the connection hole. Accordingly, the exhaustcan be prevented from leaking into a room.

In the exhaust structure for combustion apparatus described above, thecombustion apparatus is a water heater adapted to an exhaust suction andcombustion system. The water heater adapted to the exhaust suction andcombustion system can maintain the stabilized combustion state even whenthe exhaust tube is decreased in diameter.

The foregoing and other objects, features, aspects and advantages of thepresent invention will become more apparent from the following detaileddescription of the present invention when taken in conjunction with theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram schematically showing the state where an exhauststructure for combustion apparatus in one embodiment of the presentinvention is placed in a building.

FIG. 2 is a partially cutaway perspective view showing, in an enlargedmanner, a region II in FIG. 1.

FIG. 3 is a cross-sectional view showing, in an enlarged manner, aregion III in FIG. 1.

FIG. 4 is a perspective view schematically showing the configuration ofa fixing member included in the exhaust structure for combustionapparatus in one embodiment of the present invention.

FIG. 5 is a cross-sectional view schematically showing the configurationof a modification of the fixing member included in the exhaust structurefor combustion apparatus in one embodiment of the present invention.

FIG. 6 is a cross-sectional view showing, in an enlarged manner, aregion VI in FIG. 1.

FIG. 7 is a front view schematically showing the configuration of awater heater as an example of a combustion apparatus included in theexhaust structure for combustion apparatus in one embodiment of thepresent invention.

FIG. 8 is a partial cross-sectional side view schematically showing theconfiguration of the water heater shown in FIG. 7.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Embodiments of the present invention will be hereinafter described withreference to the drawings.

An exhaust structure for a combustion apparatus in one embodiment of thepresent invention will be first described.

Referring to FIG. 1, an exhaust structure for combustion apparatus 100in the present embodiment mainly has a combustion apparatus 1, anexhaust tube 20, an exhaust pipe 30, an exhaust adapter 40, a fixingmember 50, a connection pipe 60, and an exhaust terminal (a rain cap)70. This exhaust structure for combustion apparatus 100 serves to emitcombustion gas produced in combustion apparatus 1 to the outside of abuilding 200.

Combustion apparatus 1 is placed inside building 200. This combustionapparatus 1 serves as a water heater that heats warm water and water,for example, with combustion gas, and may be a heating apparatus or thelike that warms up the inside of the building with combustion gas.Furthermore, in the case where a water heater is used as combustionapparatus 1, this water heater may be, for example, a water heateradapted to an exhaust suction and combustion system. This water heatermay also be a water heater of a latent heat recovery type.

Referring to FIGS. 1 and 2, exhaust tube 20 has one end portion 20 a andthe other end portion 20 b. Exhaust tube 20 is connected to combustionapparatus 1 at one end portion 20 a. The other end portion 20 b ofexhaust tube 20 extends to the outside of the building. The inside ofexhaust tube 20 is defined as an emission path for the combustion gasemitted from combustion apparatus 1. Thus, the combustion gas producedin combustion apparatus 1 can be guided to the outside of the buildingthrough exhaust tube 20.

Exhaust tube 20 is implemented as a flexible pipe such as an accordionpipe, but may be a spiral pipe and the like. This allows exhaust tube 20to conform also to the shape of exhaust pipe 30 having a complicatedshape. Furthermore, since an exhaust flows through exhaust tube 20, thisexhaust tube 20 can be suitably made of a material having acidicresistance. This is because acidic drainage water may be dischargedtogether with an exhaust in the case where combustion apparatus 1 is awater heater of a latent heat recovery type as in the presentembodiment.

Accordingly, exhaust tube 20 can be made of a material having acidicresistance such as phenol resin, epoxy resin, silicone resin, fluorineresin such as polytetrafluoroethylene, unsaturated polyester resin,melamine resin, polycarbonate resin, methacryl styrene (MS) resin,methacryl resin, styrene acrylonitrile copolymer (AS) resin, ABS resin,polyethylene, polypropylene, polystyrene, polyethylene terephthalate(PET), and vinyl chloride resin, for example.

Exhaust pipe 30 is attached to building 200 so as to extend from theinside to the outside, for example, through a roof 210 of building 200.Exhaust pipe 30 may extend from the inside to the outside through awall. Exhaust pipe 30 is greater in outer diameter than exhaust tube 20.In the inside of this exhaust pipe 30, a part of exhaust tube 20 on theside of the other end portion 20 b is inserted. Exhaust pipe 30 isformed of metal, for example. Exhaust pipe 30 is connected to fixingmember 50 at one end portion 30 a shown in FIG. 3. Furthermore, exhaustpipe 30 is connected to exhaust terminal 70 at the other end portion 30b.

Exhaust adapter 40 is located on the other end portion 20 b side ofexhaust tube 20 and also on the other end portion 30 b side of exhaustpipe 30. Exhaust adapter 40 has an annular shape that surrounds athrough hole. Exhaust adapter 40 is attached to the outercircumferential surface of exhaust tube 20 and also to the innercircumferential surface of exhaust pipe 30 by inserting exhaust tube 20into the through hole. Specifically, this exhaust adapter 40 is fittedon the outer circumferential surface of exhaust tube 20 and fitted onthe inner circumferential surface of exhaust pipe 30. Exhaust adapter 40has an inner circumferential surface that presses the outercircumferential surface of exhaust tube 20 in the state where thisexhaust adapter 40 is fitted on the outer circumferential surface ofexhaust tube 20; and an outer circumferential surface that presses theinner circumferential surface of exhaust pipe 30 in the state whereexhaust adapter 40 is fitted on the inner circumferential surface ofexhaust pipe 30.

Consequently, the inner circumferential surface of exhaust adapter 40comes into close contact with the outer circumferential surface ofexhaust tube 20 while the outer circumferential surface of exhaustadapter 40 comes into close contact with the inner circumferentialsurface of exhaust pipe 30. Accordingly, exhaust adapter 40 can fixexhaust tube 20 to exhaust pipe 30, and also, can prevent combustion gasor drainage water from leaking through between exhaust tube 20 andexhaust pipe 30 and flowing back into the room.

The above-described configuration can be readily achieved, for example,by exhaust adapter 40 made of an elastic material. This elastic materialis for example preferably a soft resin, or for example preferably EPDM(Ethylene-Propylene-Diene Monomer), soft PVC (polyvinyl chloride),silicone rubber, fluororubber, chloroprene rubber (CR), butyl rubber(IIR), or the like. Furthermore, exhaust adapter 40 may be made of onetype elastic material, or may be made of a combination of a plurality ofdifferent types of elastic materials.

Referring to FIGS. 1 and 3, fixing member 50 serves to fix exhaust tube20 to exhaust pipe 30. Fixing member 50 fixes exhaust tube 20 to exhaustpipe 30 in the state where it is attached to the outer circumferentialsurface of exhaust tube 20. Fixing member 50 is attached to exhaust pipe30 at a position close to combustion apparatus 1 relative to exhaustadapter 40. Furthermore, fixing member 50 fixes connection pipe 60 toexhaust pipe 30.

Fixing member 50 is formed of an elastic body. This elastic body is forexample preferably made of a soft resin, or for example preferably EPDM(Ethylene-Propylene-Diene Monomer), soft PVC (polyvinyl chloride),silicone rubber, fluororubber, chloroprene rubber (CR), butyl rubber(IIR), or the like. Furthermore, fixing member 50 may be made of onetype elastic material, or may be made of a combination of a plurality ofdifferent types of elastic materials.

Referring to FIGS. 3 and 4, fixing member 50 is formed in a tubularshape. Fixing member 50 mainly has a first fixing portion 50 a, a secondfixing portion 50 b, a third fixing portion 50 c, and a main bodyportion 50 d.

First fixing portion 50 a is formed in a tubular shape. Specifically,first fixing portion 50 a has a cylindrical tubular shape. First fixingportion 50 a extends from main body portion 50 d toward combustionapparatus 1 shown in FIG. 1. It is to be noted that first fixing portion50 a may extend from main body portion 50 d toward exhaust terminal 70shown in FIG. 1.

First fixing portion 50 a is attached to exhaust tube 20. Specifically,exhaust tube 20 is introduced into a cylindrical through hole of firstfixing portion 50 a, and the inner circumferential surface of firstfixing portion 50 a is in contact with the outer circumferential surfaceof exhaust tube 20. In other words, first fixing portion 50 a is fittedaround exhaust tube 20. First fixing portion 50 a is formed to have aninner diameter smaller than the outer diameter of exhaust tube 20,thereby allowing exhaust tube 20 to be fixed with the elastic force offirst fixing portion 50 a. In the present embodiment, a binding band 51is tightened to squeeze the outer circumferential surface of firstfixing portion 50 a, so that the inner circumferential surface of firstfixing portion 50 a is brought firmly into contact with the outercircumferential surface of exhaust tube 20. Thereby, exhaust tube 20 canbe firmly fixed by first fixing portion 50 a.

Second fixing portion 50 b is formed in a tubular shape. Specifically,second fixing portion 50 b has a cylindrical tubular shape. Secondfixing portion 50 b is located outside of first fixing portion 50 a inthe radial direction of fixing member 50. Second fixing portion 50 bextends to the side opposite to the direction in which first fixingportion 50 a extends. In other words, second fixing portion 50 b extendsfrom main body portion 50 d toward exhaust terminal 70 shown in FIG. 1.

Second fixing portion 50 b is attached to exhaust pipe 30. Specifically,a part of exhaust pipe 30 on the side of one end portion 30 a isintroduced into a cylindrical through hole of second fixing portion 50b, and the inner circumferential surface of second fixing portion 50 bis in contact with the outer circumferential surface of exhaust pipe 30.In other words, second fixing portion 50 b is fitted around exhaust pipe30. Second fixing portion 50 b is formed to have an inner diametersmaller than the outer diameter of exhaust pipe 30, thereby allowingexhaust pipe 30 to be fixed with the elastic force of second fixingportion 50 b. In the present embodiment, a binding band 51 is tightenedto squeeze the outer circumferential surface of second fixing portion 50b, so that the inner circumferential surface of second fixing portion 50b is brought firmly into contact with the outer circumferential surfaceof exhaust pipe 30. Thereby, exhaust pipe 30 can be firmly fixed bysecond fixing portion 50 b.

It is to be noted that second fixing portion 50 b may be fitted insideexhaust pipe 30. In this case, second fixing portion 50 b is formed tohave an outer diameter larger than the inner diameter of exhaust pipe30, thereby allowing exhaust pipe 30 to be fixed with the elastic forceof second fixing portion 50 b.

Third fixing portion 50 c is formed in a tubular shape. Specifically,third fixing portion 50 c has a cylindrical tubular shape. Third fixingportion 50 c is located outside of first fixing portion 50 a in theradial direction of fixing member 50. Furthermore, third fixing portion50 c is located outside of second fixing portion 50 b in the radialdirection of fixing member 50. Third fixing portion 50 c extends to theside opposite to the direction in which second fixing portion 50 bextends. In other words, third fixing portion 50 c extends from mainbody portion 50 d toward combustion apparatus 1 shown in FIG. 1.

Third fixing portion 50 c is attached to connection pipe 60.Specifically, a part of connection pipe 60 on the side of the other endportion 60 b is introduced into a cylindrical through hole of thirdfixing portion 50 c, and the inner circumferential surface of thirdfixing portion 50 c is in contact with the outer circumferential surfaceof connection pipe 60. In other words, third fixing portion 50 c isfitted around connection pipe 60. Third fixing portion 50 c is formed tohave an inner diameter smaller than the outer diameter of connectionpipe 60, thereby allowing connection pipe 60 to be fixed with theelastic force of third fixing portion 50 c. In the present embodiment,binding band 51 is tightened to squeeze the outer circumferentialsurface of third fixing portion 50 c, so that the inner circumferentialsurface of third fixing portion 50 c is brought firmly into contact withthe outer circumferential surface of connection pipe 60. Thereby,connection pipe 60 can be firmly fixed by third fixing portion 50 c.

It is to be noted that third fixing portion 50 c may be fitted insideconnection pipe 60. In this case, third fixing portion 50 c is formed tohave an outer diameter larger than the inner diameter of connection pipe60, thereby allowing connection pipe 60 to be fixed with the elasticforce of third fixing portion 50 c.

Main body portion 50 d connects first fixing portion 50 a and secondfixing portion 50 b. Furthermore, main body portion 50 d connects secondfixing portion 50 b and third fixing portion 50 c. Main body portion 50d has an annular portion leading to first fixing portion 50 a; and aplate-shaped portion leading to this annular portion and second fixingportion 50 b. Furthermore, the plate-shaped portion also leads to thirdfixing portion 50 c.

Main body portion 50 d has a communication hole 50 e. The number ofcommunication holes 50 e may be one, or may be two or more. In thepresent embodiment, a plurality of communication holes 50 e areprovided. Each communication hole 50 e allows communication between afirst region R1 and a second region R2 separated from first region R1 bymain body portion 50 d. First region R1 is located between the outercircumferential surface of exhaust tube 20 and the inner circumferentialsurface of exhaust pipe 30. In the present embodiment, communicationhole 50 e is provided in the plate-shaped portion and penetrates throughmain body portion 50 d in the direction in which exhaust tube 20 extends(in the axial direction). Furthermore, communication hole 50 e alsoextends in the circumferential direction of main body portion 50 d.

Communication hole 50 e is provided in the radial direction of fixingmember 50 between the outer circumferential surface of first fixingportion 50 a and the inner circumferential surface of second fixingportion 50 b. Furthermore, communication hole 50 e is provided in theradial direction of fixing member 50 between the outer circumferentialsurface of first fixing portion 50 a and the inner circumferentialsurface of third fixing portion 50 c.

First fixing portion 50 a and second fixing portion 50 b areconcentrically arranged. Accordingly, exhaust tube 20 and exhaust pipe30 are also concentrically arranged. Furthermore, third fixing portion50 c is also arranged concentrically with first fixing portion 50 a andsecond fixing portion 50 b. Accordingly, connection pipe 60 is alsoarranged concentrically with exhaust tube 20 and exhaust pipe 30.

Referring to FIG. 5, a modification of fixing member 50 in the presentembodiment will then be described. In this modification, fixing member50 has a plurality of slits 50 f. Specifically, first fixing portion 50a is provided with a plurality of slits 50 f. Each of these slits 50 fis formed to extend from the tip end of first fixing portion 50 a towardthe bottom side thereof. Second fixing portion 50 b is also providedwith a plurality of slits 50 f. Each of these slits 50 f is formed toextend from the tip end of second fixing portion 50 b toward the bottomside thereof. It is to be noted that third fixing portion 50 c may alsobe provided with a plurality of slits 50 f as in first fixing portion 50a.

In the modification of fixing member 50 according to the presentembodiment, first fixing portion 50 a is provided with a plurality ofslits 50 f, so that the inner diameter of first fixing portion 50 a canbe increased and decreased. Accordingly, the inner diameter of firstfixing portion 50 a can be increased and decreased in accordance withthe outer diameter of exhaust tube 20. Thereby, first fixing portion 50a allows fixation of exhaust tubes 20 having a wide range of outerdiameters. Furthermore, since first fixing portion 50 a is provided witha plurality of slits 50 f, it becomes possible to suppress formation ofcreases in first fixing portion 50 a at the time when binding band 51 istightened to squeeze first fixing portion 50 a.

Furthermore, since second fixing portion 50 b is also provided with aplurality of slits 50 f, the inner diameter of second fixing portion 50b can also be increased and decreased. Accordingly, the inner diameterof second fixing portion 50 b can be increased and decreased inaccordance with the outer diameter of exhaust pipe 30. Thereby, secondfixing portion 50 b allows fixation of exhaust pipes 30 having a widerange of outer diameters. Furthermore, since second fixing portion 50 bis provided with a plurality of slits 50 f, it becomes possible tosuppress formation of creases in second fixing portion 50 b at the timewhen binding band 51 is tightened to squeeze second fixing portion 50 b.Furthermore, first fixing portion 50 a and second fixing portion 50 beach are provided with a plurality of slits 50 f, thereby allowingcombinations of exhaust tubes 20 having a wide range of outer diametersand exhaust pipes 30 having a wide range of outer diameters,respectively.

Referring to FIGS. 1 and 6, connection pipe 60 serves to cover exhausttube 20 to protect this exhaust tube 20. Connection pipe 60 is connectedto fixing member 50 and combustion apparatus 1. Connection pipe 60 isgreater in outer diameter than exhaust tube 20. A part of exhaust tube20 on the side of one end portion 20 a is introduced into connectionpipe 60.

It is to be noted that connection pipe 60 is implemented as a flexiblepipe such as an accordion pipe, but may be a spiral pipe. Connectionpipe 60 has flexibility, thereby allowing this connection pipe 60 toreadily conform to the shape of exhaust tube 20. Furthermore, connectionpipe 60 and combustion apparatus 1 can readily be connected.

Furthermore, connection pipe 60 may be a pipe made of aluminum, forexample. In this case, since connection pipe 60 can be reduced inweight, the load on fixing member 50 supporting connection pipe 60 canbe decreased. Also, since connection pipe 60 has a certain degree ofhardness, it becomes possible to suppress deformation of connection pipe60 caused by its self-weight. Furthermore, since the pipe made ofaluminum can be relatively readily processed, for example, cut and thelike, it can readily be adapted to the length of exhaust tube 20, forexample.

Second region R2 is provided between the outer circumferential surfaceof exhaust tube 20 and the inner circumferential surface of connectionpipe 60. Furthermore, combustion apparatus 1 includes a housing 9 havingan internal space. Housing 9 has a connection hole 9 aa that allowscommunication between the internal space and second region R2. Housing 9will be described later in detail.

Again referring to FIGS. 1 and 2, exhaust terminal 70 is attached to atip end of exhaust pipe 30 on the outside of the building. Exhaustterminal 70 has a circumferential wall that is provided with an exhaustport through which combustion gas is emitted to the outside (outdoors).This exhaust port allows the combustion gas guided through exhaust tube20 to be emitted from exhaust terminal 70 to the outside of building 200through exhaust pipe 30.

Exhaust terminal 70 may be an outer cover attached on the outercircumferential side of exhaust pipe 30 or may be an inner coverattached on the inner circumferential side of exhaust pipe 30. Exhaustterminal 70 is made, for example, of such a material as aluminum orstainless steel.

Combustion apparatus 1 used in exhaust structure for combustionapparatus 100 described above may be a water heater of a latent heatrecovery type, for example, adapted to an exhaust suction and combustionsystem, as described above. The configuration of the water heater of alatent heat recovery type adapted to the exhaust suction and combustionsystem will be described below.

Referring to FIGS. 7 and 8, combustion apparatus 1 mainly has a burner2, a primary heat exchanger 3, a secondary heat exchanger 4, an exhaustbox 5, a fan 6, a connection pipe 7, a drainage water tank 8, a housing9, and pipes 10 to 16.

Burner 2 serves to produce combustion gas by burning fuel gas. A gassupply pipe 11 is connected to burner 2. This gas supply pipe 11 servesto supply fuel gas to burner 2. A gas valve (not shown) implemented, forexample, by an electromagnetic valve is attached to this gas supply pipe11.

A spark plug 2 a is disposed above burner 2. This spark plug 2 a servesto ignite an air fuel mixture injected from burner 2 to thereby producea flame, by generating sparks between the plug and a target (not shown)provided in burner 2 by activating an ignition device (an igniter).Burner 2 generates a quantity of heat by burning fuel gas supplied fromgas supply pipe 11 (which is called a combustion operation).

Primary heat exchanger 3 is a heat exchanger of a sensible heat recoverytype. This primary heat exchanger 3 mainly has a plurality ofplate-shaped fins 3 b, a heat conduction pipe 3 a penetrating theplurality of plate-shaped fins 3 b, and a case 3 c accommodating fins 3b and heat conduction pipe 3 a. Primary heat exchanger 3 exchanges heatwith the combustion gas generated by burner 2, and specifically, itserves to heat hot water and water which flows through heat conductionpipe 3 a of primary heat exchanger 3 with the quantity of heat generatedas a result of the combustion operation of burner 2.

Secondary heat exchanger 4 is a heat exchanger of a latent heat recoverytype. This secondary heat exchanger 4 is located downstream of primaryheat exchanger 3 in a flow of the combustion gas and connected in serieswith primary heat exchanger 3. Since combustion apparatus 1 according tothe present embodiment thus has secondary heat exchanger 4 of a latentheat recovery type, it serves as a water heater of a latent heatrecovery type.

Secondary heat exchanger 4 mainly has a drainage water discharge port 4a, a heat conduction pipe 4 b, a sidewall 4 c, a bottom wall 4 d, and anupper wall 4 g. Heat conduction pipe 4 b is layered as it is spirallywound. Sidewall 4 c, bottom wall 4 d and upper wall 4 g are arranged tosurround heat conduction pipe 4 b.

In secondary heat exchanger 4, hot water and water which flows throughheat conduction pipe 4 b is pre-heated (heated) through heat exchangewith the combustion gas of which heat has been exchanged in primary heatexchanger 3. As a temperature of the combustion gas is lowered toapproximately 60° C. through this process, moisture contained in thecombustion gas is condensed so that latent heat can be obtained. Inaddition, latent heat is recovered in secondary heat exchanger 4 andmoisture contained in the combustion gas is condensed, whereby drainagewater is produced.

Bottom wall 4 d serves as a partition between primary heat exchanger 3and secondary heat exchanger 4, and it also serves as an upper wall ofprimary heat exchanger 3. This bottom wall 4 d is provided with anopening portion 4 e, and this opening portion 4 e allows communicationbetween a space where heat conduction pipe 3 a of primary heat exchanger3 is arranged and a space where heat conduction pipe 4 b of secondaryheat exchanger 4 is arranged. As shown by hollow arrows in FIG. 8, thecombustion gas can flow from primary heat exchanger 3 to secondary heatexchanger 4 through opening portion 4 e. In this embodiment, for thesake of simplification, although one common component is employed forbottom wall 4 d of secondary heat exchanger 4 and the upper wall ofprimary heat exchanger 3, an exhaust collection and guide member may beconnected between primary heat exchanger 3 and secondary heat exchanger4.

Upper wall 4 g is provided with an opening portion 4 h, and this openingportion 4 h allows communication between the space where heat conductionpipe 4 b of secondary heat exchanger 4 is arranged and an internal spacein exhaust box 5. As shown by hollow arrows in FIG. 8, the combustiongas can flow from secondary heat exchanger 4 into the internal space inexhaust box 5 through opening portion 4 h.

Drainage water discharge port 4 a is provided in sidewall 4 c or bottomwall 4 d. This drainage water discharge port 4 a opens at a lowestposition in the space surrounded by side wall 4 c, bottom wall 4 d andupper wall 4 g (the lowermost position in the vertical direction in thestate where the water heater is placed), which is lower than thelowermost portion of heat conduction pipe 4 b. Thus, drainage waterproduced in secondary heat exchanger 4 can be guided to drainage waterdischarge port 4 a along bottom wall 4 d and sidewall 4 c as shown by ablack arrow in FIG. 8.

Exhaust box 5 forms a path for a flow of the combustion gas betweensecondary heat exchanger 4 and fan 6. This exhaust box 5 can guide, tofan 6, the combustion gas of which heat has been exchanged in secondaryheat exchanger 4. Exhaust box 5 is attached to secondary heat exchanger4 and located downstream of secondary heat exchanger 4 in the flow ofthe combustion gas.

Exhaust box 5 mainly has a box main body 5 a and a fan connectionportion 5 b. An internal space in box main body 5 a communicates throughopening portion 4 h in secondary heat exchanger 4 with the internalspace where heat conduction pipe 4 b of secondary heat exchanger 4 isarranged. Fan connection portion 5 b is provided so as to protrude froman upper portion of box main body 5 a. This fan connection portion 5 bhas, for example, a cylindrical shape, and an internal space 5 bathereof communicates with the internal space in box main body 5 a.

Fan 6 serves to emit the combustion gas (of which heat has beenexchanged in secondary heat exchanger 4), which has passed throughsecondary heat exchanger 4, to the outside of combustion apparatus 1 bysuctioning the combustion gas. This fan 6 is located downstream ofexhaust box 5 and secondary heat exchanger 4 in the flow of thecombustion gas. Namely, in combustion apparatus 1, burner 2, primaryheat exchanger 3, secondary heat exchanger 4, exhaust box 5, and fan 6are arranged in this order from upstream to downstream in the flow ofthe combustion gas produced in burner 2. Since the combustion gas issuctioned and exhausted by means of fan 6 as above in this arrangement,combustion apparatus 1 in the present embodiment is a water heateradapted to the exhaust suction and combustion system.

Fan 6 mainly has a rotor 6 a, a fan case 6 b, a drive source 6 c, and arotation shaft 6 d. Fan case 6 b is attached to fan connection portion 5b of exhaust box 5 such that the internal space in fan case 6 b and theinternal space in fan connection portion 5 b communicate with eachother. Thus, as shown by the hollow arrows in FIG. 8, the combustion gascan be suctioned from box main body 5 a of exhaust box 5 through fanconnection portion 5 b into fan case 6 b.

Rotor 6 a is arranged in fan case 6 b. This rotor 6 a is connected todrive source 6 c with rotation shaft 6 d interposed therebetween. Thus,rotor 6 a is provided with drive force from drive source 6 c and canrotate around rotation shaft 6 d. By rotation of rotor 6 a, thecombustion gas in exhaust box 5 can be suctioned from the innercircumferential side of rotor 6 a and can be emitted to the outercircumferential side of rotor 6 a.

Connection pipe 7 is connected to a region within fan case 6 b, on theouter circumferential side of a region where rotor 6 a is arranged.Therefore, the combustion gas emitted to the outer circumferential sideof rotor 6 a by rotor 6 a of fan 6 can be emitted into exhaust tube 20through connection pipe 7.

The combustion gas produced by burner 2 as above is suctioned by fan 6by rotation of rotor 6 a above, so that the combustion gas can reach fan6 after passage through primary heat exchanger 3, secondary heatexchanger 4 and exhaust box 5 in this order as shown by the hollowarrows in FIG. 8 and can be emitted to the outside of combustionapparatus 1.

Drainage water tank 8 serves to store drainage water produced insecondary heat exchanger 4. This drainage water tank 8 is connected tosecondary heat exchanger 4 through pipe 10. Pipe 10 is connected todrainage water discharge port 4 a of secondary heat exchanger 4. Thus,the drainage water produced in secondary heat exchanger 4 can bedischarged to drainage water tank 8. A pipe 15 extending to the outsideof combustion apparatus 1 is connected to drainage water tank 8. Thedrainage water stored in drainage water tank 8 can be discharged to theoutside of combustion apparatus 1 through this pipe 15.

This drainage water tank 8 has a water seal structure. Namely, drainagewater tank 8 has such a structure that, when a prescribed amount ofdrainage water is stored in drainage water tank 8, the stored drainagewater cannot allow air to pass through drainage water tank 8. By such awater seal structure of drainage water tank 8, entry of air outsidecombustion apparatus 1 (outside air) into combustion apparatus 1(secondary heat exchanger 4) through drainage water tank 8 via pipe 15can be prevented.

It is to be noted that the lower portion of drainage water tank 8 isconnected to a pipe 16 for discharging drainage water, separately frompipe 15. This pipe 16 (usually closed) for discharging drainage water isdesigned such that drainage water within drainage water tank 8 thatcannot be discharged through pipe 15 can be discharged by opening thispipe 16 during maintenance and the like. Furthermore, drainage watertank 8 has an internal space that may contain a neutralizing agent (notshown) for neutralizing acidic drainage water.

A water supply pipe 12 is connected to one end of heat conduction pipe 4b of secondary heat exchanger 4 and a hot water delivery pipe 13 isconnected to one end of heat conduction pipe 3 a of primary heatexchanger 3. The other end of heat conduction pipe 3 a of primary heatexchanger 3 and the other end of heat conduction pipe 4 b of secondaryheat exchanger 4 are connected to each other through a pipe 14. Each ofgas supply pipe 11, water supply pipe 12 and hot water delivery pipe 13described above leads to the outside, for example, in a top portion ofcombustion apparatus 1. Burner 2, primary heat exchanger 3, secondaryheat exchanger 4, exhaust box 5, fan 6, drainage water tank 8, and thelike are arranged in housing 9.

Again referring to FIGS. 6 and 7, housing 9 has a connection portion 9 aand an exhaust portion 9 b. Specifically, housing 9 has an upper surfaceprovided with tubular connection portion 9 a and tubular exhaust portion9 b that are concentrically arranged and protrude in the upwarddirection. In other words, connection portion 9 a and exhaust portion 9b form a double-pipe structure.

Connection portion 9 a is provided so as to surround the outercircumferential surface of exhaust portion 9 b. Furthermore, connectionhole 9 aa is provided in a region of housing 9 between the outercircumferential surface of exhaust portion 9 b and the innercircumferential surface of connection portion 9 a. An exhaust port 9 bbis provided inside exhaust portion 9 b of housing 9. Connection hole 9aa communicates with the inside of housing 9 while exhaust port 9 bbcommunicates with the inside of connection pipe 7. Accordingly, secondregion R2 provided between the outer circumferential surface of exhausttube 20 and the inner circumferential surface of connection pipe 60communicates with the internal space of housing 9 through connectionhole 9 aa provided in housing 9. Furthermore, the combustion gas havingflown through burner 2 is sent from connection pipe 7 to exhaust tube 20via exhaust portion 9 b.

Connection portion 9 a is connected to connection pipe 60 on the one endportion 60 a side thereof while exhaust portion 9 b is connected toexhaust tube 20 on the one end portion 20 a side thereof. In addition,exhaust portion 9 b is connected also to connection pipe 7 housed withinhousing 9. For example, exhaust portion 9 b is formed to protrude alsodownward in a tubular manner from the upper surface of housing 9, sothat exhaust portion 9 b and connection pipe 7 can be readily connectedto each other.

Connection portion 9 a and connection pipe 60 only have to be connectedto each other so as to prevent leakage of the gas flowing therethrough.Similarly, exhaust portion 9 b and exhaust tube 20 (and connection pipe7) only have to be connected to each other so as to prevent leakage ofthe gas flowing therethrough. Accordingly, an O-ring may be interposedbetween these components connected to each other, or these componentsmay be firmly bound using a binding band. It is to be noted thatconnection between these components may be implemented by an inner coveror an outer cover.

Then, the functions and effects of the present embodiment will bedescribed.

As described above, in the case where combustion apparatus 1 alreadyplaced inside the building is replaced with a new combustion apparatus1, the already-placed exhaust pipe 30 is left unremoved and a newexhaust tube 20 is inserted into this already-placed exhaust pipe 30, sothat combustion apparatus 1 can be replaced. In other words, an exhaustproduced in combustion apparatus 1 is to be guided through exhaust tube20 inserted into exhaust pipe 30, and emitted to the outside of abuilding.

In the case where a new exhaust tube 20 is inserted into thealready-placed exhaust pipe 30 from inside of the building, exhaust tube20 may fall into inside of the building from inside of exhaust pipe 30if exhaust tube 20 is merely inserted into exhaust pipe 30 but not fixedin this state.

According to exhaust structure for combustion apparatus 100 of thepresent embodiment, as shown in FIG. 3, exhaust tube 20 is fixed toexhaust pipe 30 in the state where second fixing portion 50 b of fixingmember 50 is attached to exhaust pipe 30 and first fixing portion 50 ais attached to the outer circumferential surface of exhaust tube 20.Accordingly, fixing member 50 can prevent falling of exhaust tube 20inserted into exhaust pipe 30.

Furthermore, fixing member 50 is attached to exhaust pipe 30 at aposition close to combustion apparatus 1 relative to exhaust adapter 40.Even in the case where exhaust tube 20 can be fixed to exhaust pipe 30by exhaust adapter 40, exhaust tube 20 cannot be fixed until it reachesexhaust adapter 40 since exhaust tube 20 is inserted into exhaust pipe30 from inside of the building. According to the present embodiment,since fixing member 50 is attached to exhaust pipe 30 at a positionclose to combustion apparatus 1 relative to exhaust adapter 40, fixingmember 50 can prevent falling of exhaust tube 20, which is inserted intoexhaust pipe 30, even before exhaust adapter 40 is attached.

In exhaust structure for combustion apparatus 100 according to thepresent embodiment, as shown in FIG. 3, fixing member 50 is providedwith communication hole 50 e that allows communication between firstregion R1 and second region R2. Accordingly, in the case where anexhaust leaks to first region R1 due to damage of exhaust tube 20 or thelike, the exhaust can be emitted from first region R1 to second regionR2 through communication hole 50 e.

In exhaust structure for combustion apparatus 100 according to thepresent embodiment, as shown in FIG. 3, first fixing portion 50 a andsecond fixing portion 50 b each have a cylindrical shape and areconcentrically arranged. Accordingly, when exhaust tube 20 is insertedinto exhaust pipe 30, the outer circumferential surface of exhaust tube20 is less likely to come into contact with the inner circumferentialsurface of exhaust pipe 30. Thereby, exhaust tube 20 can be readilyinserted into exhaust pipe 30.

In exhaust structure for combustion apparatus 100 according to thepresent embodiment, as shown in FIG. 1, a part of exhaust tube 20 isinserted into connection pipe 60. Accordingly, exhaust tube 20 can beprotected by connection pipe 60 from ultraviolet light or force appliedfrom outside.

Furthermore, as shown in FIG. 6, housing 9 has connection hole 9 aa thatallows communication between the internal space and second region R2that is provided between the outer circumferential surface of exhausttube 20 and the inner circumferential surface of connection pipe 60.Accordingly, in the case where damage of exhaust tube 20 or the likecauses leakage of an exhaust to first region R1 between the outercircumferential surface of exhaust tube 20 and the inner circumferentialsurface of exhaust pipe 30, this exhaust can be emitted from firstregion R1 through communication hole 50 e to second region R2 providedbetween the outer circumferential surface of exhaust tube 20 and theinner circumferential surface of connection pipe 60. Furthermore, anexhaust can be emitted from second region R2 to the internal spacethrough connection hole 9 aa. Consequently, leakage of an exhaust into aroom can be prevented.

In the exhaust structure for combustion apparatus according to thepresent embodiment, as shown in FIG. 7, combustion apparatus 1 is awater heater adapted to an exhaust suction and combustion system. Thewater heater adapted to an exhaust suction and combustion system canmaintain a stabilized combustion state even in the case where exhausttube 20 is decreased in diameter.

In other words, since combustion apparatus 1 serving as a water heateradapted to an exhaust suction and combustion system is used, thecombustion operation by burner 2 can be stabilized for the water heaterof a so-called an exhaust pushing type even in the case where exhausttube 20 is decreased in diameter, which will be hereinafter described.

In the water heater of a so-called exhaust pushing type, a fan, aburner, a primary heat exchanger, and a secondary heat exchanger arearranged in this order from upstream to downstream in the flow of thecombustion gas. In other words, the combustion gas produced by theburner is guided by the fan to flow through the primary heat exchangerand the secondary heat exchanger into the exhaust tube provided outsideof the water heater.

The combustion gas pushed out by the fan receives flow path resistancecaused by the primary heat exchanger and the secondary heat exchangerbefore this combustion gas reaches the exhaust tube. Accordingly, theblast pressure of the combustion gas immediately in front of the exhausttube is lowered by this flow path resistance. For this reason, the blastpressure caused by the fan should be raised in order to push thecombustion gas into the exhaust tube having a relatively small diameter.However, when the blast pressure of the fan is raised, the internalpressure within the burner case is raised. Consequently, in the casewhere the fuel gas is supplied to the burner at relatively low pressure,the combustion operation becomes unstable.

On the other hand, according to the exhaust suction and combustionsystem in the present embodiment, burner 2, primary heat exchanger 3,secondary heat exchanger 4, and fan 6 are arranged in this order fromupstream to downstream in the flow of the combustion gas. In thissystem, negative pressure occurs on the upstream side of fan 6, whicheliminates the need to raise the blast pressure of fan 6. Accordingly,even in the case where exhaust tube 20 is decreased in diameter, theinternal pressure within the burner case can be maintained low.Therefore, the combustion operation can be stabilized even if the fuelgas is supplied to burner 2 at relatively low pressure.

Although the present invention has been described and illustrated indetail, it is clearly understood that the same is by way of illustrationand example only and is not to be taken by way of limitation, the scopeof the present invention being interpreted by the terms of the appendedclaims.

What is claimed is:
 1. An exhaust structure for combustion apparatus,comprising: a combustion apparatus; an exhaust tube having one endportion and the other end portion, and connected to said combustionapparatus at said one end portion; an exhaust pipe, in which a part ofsaid exhaust tube on a side of said other end portion being inserted; anexhaust adapter having an annular shape surrounding a through hole, andattached to an outer circumferential surface of said exhaust tube and toan inner circumferential surface of said exhaust pipe by inserting saidexhaust tube into said through hole; and a fixing member formed of anelastic body, attached to said exhaust pipe at a position close to saidcombustion apparatus relative to said exhaust adapter, and fixing saidexhaust tube to said exhaust pipe while being attached to the outercircumferential surface of said exhaust tube.
 2. The exhaust structurefor combustion apparatus according to claim 1, wherein said fixingmember includes a first fixing portion attached to said exhaust tube, asecond fixing portion attached to said exhaust pipe, and a main bodyportion connecting said first fixing portion and said second fixingportion, and said main body portion has a communication hole that allowscommunication between a first region and a second region separated fromsaid first region by said main body portion, said first region beinglocated between the outer circumferential surface of said exhaust tubeand the inner circumferential surface of said exhaust pipe.
 3. Theexhaust structure for combustion apparatus according to claim 2, whereinsaid first fixing portion and said second fixing portion each have acylindrical shape and are concentrically arranged.
 4. The exhauststructure for combustion apparatus according to claim 2, furthercomprising a connection pipe connected to said fixing member and saidcombustion apparatus, a part of said exhaust tube on a side of said oneend portion being inserted into said connection pipe, wherein saidsecond region is provided between the outer circumferential surface ofsaid exhaust tube and an inner circumferential surface of saidconnection pipe, said combustion apparatus includes a housing having aninternal space, and said housing has a connection hole that allowscommunication between said internal space and said second region.
 5. Theexhaust structure for combustion apparatus according to claim 1, whereinsaid combustion apparatus is a water heater adapted to an exhaustsuction and combustion system.